Cupra R airflow

[DPJ]

Hi Willy

Maximum Boost - Corky Bell's book

Feel quoted me 0.85 for VE from Bell's book. I was pretty stunned to come up with the result above once I had this. I need to read the book and read up some more on VE before I can comment further.

 

[Feel]

Cool name, in't it He wrote a book called "Maximum Boost" that got recommended a while back, and I know a few people have it. If you're nerdy enough to be interested, it make a good stocking filler. Got mine off Amazon.

The book does one example calculation, where he uses 85% VE and it's never mentioned again, doesn't say where to look it up for different engines, or if 85% is typical

Thinking about it, if the cylinder fill isn't 100% efficient, then does boost in the cylinder fall by some (the same?) proportion? Although, I wonder if it's really a set percentage across the rev range - the faster the piston moves, the lower the VE??

I also wonder if losses in the system are not just to do with cylinder filling, what about other losses in the inlet - intercooler for example. The pressure ratio we calculated, maybe wasn't right - I did (1000+1940) /1000 which is MAP boost, not turbo outlet. Maybe those two counter each other...

 

[DPJ]

Cool name, in't it He wrote a book called "Maximum Boost" that got recommended a while back, and I know a few people have it. If you're nerdy enough to be interested, it make a good stocking filler. Got mine off Amazon.

The book does one example calculation, where he uses 85% VE and it's never mentioned again, doesn't say where to look it up for different engines, or if 85% is typical

Thinking about it, if the cylinder fill isn't 100% efficient, then does boost in the cylinder fall by some (the same?) proportion? Although, I wonder if it's really a set percentage across the rev range - the faster the piston moves, the lower the VE??

I also wonder if losses in the system are not just to do with cylinder filling, what about other losses in the inlet - intercooler for example. The pressure ratio we calculated, maybe wasn't right - I did (1000+1940) /1000 which is MAP boost, not turbo outlet. Maybe those two counter each other...

I'd love to try to get a handle on this together. The problem always seems to be that someone rushes too far ahead and everyone gets left behind. Perhaps we should set up something and work one stage at a time....

Where does the system measure actual pressure?

 

[wild willy]

Hi Willy

Maximum Boost - Corky Bell's book

Feel quoted me 0.85 for VE from Bell's book. I was pretty stunned to come up with the result above once I had this. I need to read the book and read up some more on VE before I can comment further.

 

[wild willy]

Cool name, in't it He wrote a book called "Maximum Boost" that got recommended a while back, and I know a few people have it. If you're nerdy enough to be interested, it make a good stocking filler. Got mine off Amazon.

The book does one example calculation, where he uses 85% VE and it's never mentioned again, doesn't say where to look it up for different engines, or if 85% is typical

Thinking about it, if the cylinder fill isn't 100% efficient, then does boost in the cylinder fall by some (the same?) proportion? Although, I wonder if it's really a set percentage across the rev range - the faster the piston moves, the lower the VE??

I also wonder if losses in the system are not just to do with cylinder filling, what about other losses in the inlet - intercooler for example. The pressure ratio we calculated, maybe wasn't right - I did (1000+1940) /1000 which is MAP boost, not turbo outlet. Maybe those two counter each other...

Its like a mini university challange (spelling)
Nothing better than calcs that add up to real world.

 

[Feel]

I'd love to try to get a handle on this together. The problem always seems to be that someone rushes too far ahead and everyone gets left behind. Perhaps we should set up something and work one stage at a time....

Where does the system measure actual pressure?

I was thinking earlier this might get some more learned attention if it was in the turbo tuning forum...

The MAP Sensor is between the intercooler outlet and the throttle body. I understand that the ECU uses the MAP and the MAF to calculate the inlet manifold pressure - it's on a block in VAG-COM somewhere...

 

[Feel]

Calculating your VE from measured MAF readings:

http://www.installuniversity.com/in...metric_efficiency/ve_computation_9.012000.htm

Haven't really read it, but since you've got your calculated MAF very clsoe to your actually MAF using 85% VE, then going the other way round would yield a VE very close to 85%. A quick bit of googling shows people using 80-90% as typical VE.

 

[DPJ]

I was thinking earlier this might get some more learned attention if it was in the turbo tuning forum...
...

If Exhaust manifold swap doesn't take all weekend, I might re-start this as a thread there (I agree with you)

Calculating your VE from measured MAF readings:
.

Good one Phil. I'll read that again tomorrow. Unfortunately it assumes the MAF is reading accurately, which is where this thread came in. The problems appear when people start to doubt their MAF readings.

 

[Feel]

Yeah, be VE is going to be consistent for our engines?

 

[DPJ]

Yeah, be VE is going to be consistent for our engines?

Probably yes. 20VT head, same valves (same cams?) same ports, same stroke and bore, the only thing someone mentioned recently that I haven't checked (correct me if I'm wrong) is compression ratio which would be down to piston crown shape.

I think CRs are the same on 180 and 210/225 engines, but I'll stand corrected.

The inlet manifolds have a bearing, but you could take that into account under actual boost pressure contained, rather than VE.????

 

[YerMother]

Compression ratios are different from the 180 to the 225 so the VE will be different from the two engines as the stroke is different with the same turbo!

 

[DPJ]

AUQ Bore 81mm stroke 86.4mm CR 9.5:1
BAM Bore 81mm stroke 86.4mm CR 9.5:1

I'm struggling to find stats that say any different.

Edit: however - a search on TTs and the S3 225 is bringing up 9.0:1

 

[martin CR]

AUQ Bore 81mm stroke 86.4mm CR 9.5:1
BAM Bore 81mm stroke 86.4mm CR 9.5:1

I'm struggling to find stats that say any different.

Edit: however - a search on TTs and the S3 225 is bringing up 9.0:1

The stroke is the same, I think they bring the CR down with different pistons on the 210/225

 

[Feel]

Yeah, I was puzzling the difference.

1) Does the CR effect VE?

2) I'd understood that the pistons were the same (only from reading forums, never actually seen any) if they are, and bore and stroke are the same, what makes the CR different? Head gasket or Head?

 

[DPJ]

Yeah, I was puzzling the difference.

1) Does the CR effect VE?

2) I'd understood that the pistons were the same (only from reading forums, never actually seen any) if they are, and bore and stroke are the same, what makes the CR different?

This article reckons CR has very little effect on VE.

The only thing that would make CR different between LC and LCR would be pistons being less tall crown to pin on the LCR or a more indented crown. (or a thicker head gasket (unlikely) on the LCR.......

 

[Feel]

CR/VE - Guessed as much.

Common knowledge is that CR is definitely different, but i can't find much info and how they are different...

 

[YerMother]

CR on 225 is 8.5:1 i thought!! Defo lower ratio on the 210/225 unit

 

[martin CR]

CR on 225 is 8.5:1 i thought!! Defo lower ratio on the 210/225 unit

The CR is 9.5:1 on the AMK,APY and BAM engine, Bore is 81mm and Stroke 86.4mm, well thats what the Audi service manual says it is.

 

[Feel]

I found this URL scribbled on a piece of paper in my Corky Bell book - very useful:

http://www.turbobygarrett.com/turbobygarrett/tech_center/tech_center.html

 

[DPJ]

I found this URL scribbled on a piece of paper in my Corky Bell book - very useful:

http://www.turbobygarrett.com/turbobygarrett/tech_center/tech_center.html

A few interesting things there.

What is my mass flow rate? As a very general rule, turbocharged gasoline engines will generate 9.5-10.5 horsepower (as measured at the flywheel) for each lb/min of airflow. So, an engine with a target peak horsepower of 400 Hp will require 36-44 lb/min of airflow to achieve that target. This is just a rough first approximation to help narrow the turbo selection options.

So to convert to metric, 1gram of air per sec would generate approximately 1.256 to 1.389 bhp.

Engine Volumetric Efficiency. Typical numbers for peak Volumetric Efficiency (VE) range in the 95%-99% for modern 4-valve heads, to 88% - 95% for 2-valve designs. If you have a torque curve for your engine, you can use this to estimate VE at various engine speeds. On a well-tuned engine, the VE will peak at the torque peak, and this number can be used to scale the VE at other engine speeds. A 4-valve engine will typically have higher VE over more of its rev range than a two-valve engine

That's peak VE (at peak torque). Does Corky Bell's book show any VE graphs, Phil?